The invention relates generally to nucleic acids and polypeptides and more particularly to nucleic acids encoding polypeptides related to previously described angiogenesis-modulating polypeptides, and to the polypeptides encoded by these nucleic acids.
Under normal physiological conditions, humans or animals undergo angiogenesis, i.e., generation of new blood vessels into a tissue or organ, only in restricted situations. During angiogenesis, endothelial cells react to stimulation with finely tuned signaling responses. The xe2x80x9cendotheliumxe2x80x9d is a thin layer of flat epithelial cells that lines serous cavities, lymph vessels, and blood vessels. In normal physiological states such as embryonic growth and wound healing, neovascularization is controlled by a balance of stimulatory and inhibitory angiogenic factors. These controls may fail and result in formation of an extensive capillary network during the development of many diseases including ischemic heart disease, ischemic peripheral vascular disease, tumor growth and metastasis, reproduction, embryogenesis, wound healing, bone repair, rheumatoid arthritis, diabetic retinopathy and other diseases.
Both controlled and uncontrolled angiogenesis are thought to proceed in a similar manner. Endothelial cells and pericytes, surrounded by a basement membrane, form capillary blood vessels. Angiogenesis begins with the erosion of the basement membrane by enzymes released by endothelial cells and leukocytes. The endothelial cells, which line the lumen of blood vessels, then protrude through the basement membrane. Angiogenic stimulants induce the endothelial cells to migrate through the eroded basement membrane. The migrating cells form a xe2x80x9csproutxe2x80x9d off the parent blood vessel, where the endothelial cells undergo mitosis and proliferate. The endothelial sprouts merge with each other to form capillary loops, creating the new blood vessel.
Persistent, unregulated angiogenesis occurs in a multiplicity of disease states, tumor metastasis and abnormal growth by endothelial cells and supports the pathological damage seen in these conditions. The diverse pathological disease states in which unregulated angiogenesis is present have been grouped together as angiogenic dependent or angiogenic associated diseases.
The balance of positive or negative angiogenesis regulators control the fate of vascular wall cells. They remain either in a state of vascular homeostasis, or they proceed to neovascularization, e.g., tumor growth and the switch to an angiogenic tumor phenotype correlates with increased secretion of angiogenic molecules such as fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), and others. On the other hand, tumors also acquire a more angiogenic phenotype because inhibitors of angiogenesis are down-regulated during tumorigenesis (e.g. thrombospondin)(Dameron et al., 1994, Science 265:1582-1584).
Angiogenic and antiangiogenic (or angiostatic) molecules control the formation of new vessels via different mechanisms. Antiangiogenic molecules, or angiogenesis inhibitors (e.g. angiostatin, angiopoeitin-1 (Ang11), rat microvascular endothelial differentiation gene (MEDG), somatostatin, thrombospondin, platelet factor 4) can repress angiogenesis, and therefore, maintain vascular homeostasis (see, e.g. for review Bicknell, 1994, Ann. Oncol. 5 (suppl) 4:45-50).
Angiogenic molecules are capable of inducing the formation of new vessels and include, for example, but not for limitation, fibroblast growth factor (FGF), angiopoeitin 2 (Ang-2), erythroipoietin, hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF) and others (for review, see e.g. Folkman and Shing, 1992, J. Biol. Chem. 267:10931-10934). FGF elicit its effects mainly via direct action on relevant endothelial cells via its endothelial receptor (e.g. Folkman and Shing, 1992, J. Biol. Chem. 267:10931-10934). FGF lacks a signal sequence for secretion.
Angiogenesis has been implicated in ischemic heart and ischemic vascular disease. In myocardial infarction new vessels penetrate the necrotic area and the surrounding schemic tissue. Neovascularizations, together with inflammatory cells, remove cellular debris and play a role in tissue repair and remodeling that results in myocardial scar formation. FGF-induced mycoardial infarction and neovascularization (e.g. Yanagisawa-Miwa et al., 1992, Science 257:1401-1403; Harada et al., 1994, J. Clin. Invest. 94:623-630) show that angiogenesis contributes to the preservation of ischemic tissue and myocardial pump function in myocardial necrosis. This suggests a therapeutic use of angiogenic factors in clinical situations. Additional studies with FGF (Pu et al., 1993, Circulation 88:208-215) and VEGF (Takeshita et al., 1994, J. Clin. Invest 93:662-670) in peripheral ischemic vascular disease protected ischemic limbs. Similar to myocardial infarction, brain infarcts (strokes) are associated with angiogenesis (Chen et al., 1994, Stroke 25-1651-1657).
Likewise, angiogenesis has been implicated in various cancers. Angiogenesis is an essential component of the metastatic pathway (see, e.g. Zetter, 1998, Ann. Rev. Med. 49:407-427). These blood vessels provide the principal pathway by which tumor cells exit the primary tumor site and enter the circulation. Tumor angiogenesis is regulated by the production of angiogenic stimulators including members of the FGF and VEGF families (see, e.g. Fernig and Gallaher, 1994, Prog. Growth Factor Res. 5:353-377). Tumors may also activate angiogenic inhibitors such as angiostatin (U.S. Pat. No. 5,639,725, herein incorporated by reference) and endostatin that can modulate angiogenesis both at the primary site and at downstream sites of metastasis. The potential use of these and other natural and synthetic angiogenic inhibitors as anticancer drugs is currently under intense investigation (see, e.g. Zetter, 1998, Ann. Rev. Med. 49:407-427). Such agents may have reduced toxicity and be less likely to generate drug resistance than conventional cytotoxic drugs. Clinical trials are now underway to develop optimum treatment strategies for antiangiogenic agents.
Angiopoietin-1 (Ang-1) is an angiogenic factor that signals through the endothelial cell-specific Tie2 receptor tyrosine kinase. Like VEGF, Ang- I is essential for normal endothelial developmental processes in the mouse (Davis et al., 1996, Cell 87:). Furthermore, Ang-1 induces the formation of capillary sprouts (Koblizek et al., 1998, Curr. Biol. 8:529-532). The protein is expressed only on endothelial cells and early hemopoietic cells (e.g., see Sure et al., 1996, Cell 87:1171-1180).
Angiopoietin-2 (Ang-2) is a naturally occurring antagonist for Ang1 and Tie2 and can disrupt blood vessel formation in the mouse embryos (see, eg. Maisonpierre et al., 1997, Science 277:55-). Ang-2 is expressed only at sites of vascular remodeling.
In animal models some angiogenesis-dependent diseases can be controlled via induction or inhibition of new vessel formation. Treatment of diseases by modulation of angiogenesis are currently tested in clinical trials. Thus the manipulation of new vessel formation in angiogenesis-dependent conditions such as wound healing, inflammatory diseases, ischemic heart and peripheral vascular disease, myocardial infarction, diabetic retinopathy, and cancer is likely to create new therapeutic options.
Thus, angiogenesis is believed to play a significant role in the metastasis of a cancer and in the ischemic heart and ischemic vascular disease. If this angiogenic activity could be repressed or eliminated, then the tumor, although present, would not grow. In the disease state, prevention of angiogenesis could avert the damage caused by the invasion of the new microvascular system. If this angiogenic activity could be stimulated or induced, ischemic tissues in the heart and brain and mycocardial necrosis could be prevented. In the disease state, stimulation or induction of angiogenesis could avert the damage. Therapies directed at control of the angiogenic processes could lead to the abrogation or mitigation of these diseases.
Novel angiogenic and antiangiogenic molecules are needed, both to model unwanted growth of blood vessels, especially into tumors, and for therapies directed to preventing such unwanted growth. In certain antiangiogenic embodiments, the compositions and methods of this invention are useful in inhibiting the activity of endogenous growth factors in premetastatic tumors and preventing the formation of the capillaries in the tumors thereby inhibiting the growth of the tumors. The composition, and antibodies specific to the composition, should also be able to modulate the formation of capillaries in other angiogenic processes, such as wound healing and reproduction. Finally, the composition and method for inhibiting angiogenesis should preferably be non-toxic and produce few side effects.
The present invention is directed to novel molecules, referred to herein as xe2x80x9cangiopoeitin-3 (Ang-3)xe2x80x9d, xe2x80x9chuman microvascular endothelial differentiation gene 1 (hMEDG1)xe2x80x9d and xe2x80x9cheart specific growth factor-8b (FGF-8b)xe2x80x9d polypeptides, as well as nucleic acid sequences encoding those molecules.
In certain preferred embodiments, the novel nucleic acid sequences of this invention is operatively linked to one or more expression control sequences. The invention also provides a host cell, including bacterial, plant, yeast, insect and mammalian cells, that produce the novel polypeptides, whether the cell is transformed with the nucleic acid sequences encoding those proteins, or whether the cell is transformed with regulatory sequences to activate or enhance production of these proteins from an endogenous nucleic acid sequence encoding same.
Processes are also provided for producing a protein, which comprise growing a culture of host cells producing such proteins (as described above) in a suitable culture medium, and purifying the protein from the culture. The protein produced according to such methods is also provided by the present invention. In preferred embodiments the protein comprises an angiopoeitin-3, hMEDG1 and FGF-8b amino acid sequence or fragments thereof, the protein being substantially free from other mammalian proteins. Such compositions may further comprise a pharmaceutically acceptable carrier. Compositions comprising an antibody which specifically reacts with such protein are also contemplated by the present invention. Methods are also contemplated for preventing, treating or ameliorating a medical condition which comprises administering to a mammalian subject a therapeutically effective amount of a composition comprising a protein of the present invention and a pharmaceutically acceptable carrier.
In certain angiogenic embodiments, the compositions and methods of this invention are useful in stimulating the growth of blood vessels, especially in mycocardial infarction and other heart diseases or brain infarcts (strokes). The composition should be able to overcome the necrotic effects of ischemic tissue and thereby prevent the effects of heart diseases or strokes. Finally, the composition and method for stimulating angiogenesis should preferably be non-toxic and produce few side effects.
The proteins disclosed in this invention are likely to play a role in angiogenesis. Accordingly, the compositions and methods of this invention are useful in anti-cancer and heart disease therapies. Diagnostic, prognostic and screening kits are also contemplated.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In the case of conflict, the present Specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.
Other features and advantages of the invention will be apparent from the following detailed description and claims.